Hello, On Tue, Sep 04, 2012 at 09:54:23AM -0400, Vivek Goyal wrote: > > Given that we are working around stack depth issues in the > > filesystems already in several places, and now it seems like there's > > a reason to work around it in the block layers as well, shouldn't we > > simply increase the default stack size rather than introduce > > complexity and performance regressions to try and work around not > > having enough stack? > > Dave, > > In this particular instance, we really don't have any bug reports of > stack overflowing. Just discussing what will happen if we make > generic_make_request() recursive again. I think there was one and that's why we added the bio_list thing. > > I mean, we can deal with it like the ia32 4k stack issue was dealt > > with (i.e. ignore those stupid XFS people, that's an XFS bug), or > > we can face the reality that storage stacks have become so complex > > that 8k is no longer a big enough stack for a modern system.... > > So first question will be, what's the right stack size? If we make > generic_make_request() recursive, then at some storage stack depth we will > overflow stack anyway (if we have created too deep a stack). Hence > keeping current logic kind of makes sense as in theory we can support > arbitrary depth of storage stack. But, yeah, this can't be solved by enlarging the stack size. The upper limit is unbound. Thanks. -- tejun -- dm-devel mailing list dm-devel@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/dm-devel
